@ Karmington thanks for your comment.
When I started doing these tutorials, I thought it will be easier to write. In the end it turned out like this: a general description of the games / source code and source code itself for "experimentation". "Fortunately", some prefer to learn by experimenting, add or edit an already existing code.
The Duck tutorial contains some magic numbers, for example, in the duckLines array. But for the duck image I always use the function which returns the width of the image (duckImg.getWidth ()). I just looked at the code and saw that when I check whether any of the ducks was hit that I used seven "magic" numbers. I will repair this when I will have time.
As regards a resolution, I did not want a player to change the window size during the game, it would then have to change some variables and then there would be more code that would not be connected to the topic of tutorial(moving object). For the first game / tutorial is enough to teach the user to move objects. Adjusting the game to different resolutions would be the topic for another tutorial.
I did not know that this section is only to have a full article.
Thank you for adding link under the 'Java Gaming Resources' page. But the user that is written in brackets is wrong.
Sorry for my bad English.